Signatures of alternative models beyond the Standard Model 이강영 ( 건국대학교 연세대학교

Contents Introduction Z’ W’ H + H ++ t’, b’ Q, L Dark matter Summary

Introduction LHC will explore for the first time a relevant energy range, well above the Fermi scale. LHC is the Energy frontier machine best to search for the new (heavy) particles. We concentrate on the new particles discovery. The detailed phenomenology depends upon the model.

 2008 년 9 월 10 일 공식적으로 가동.  올 11 월부터 정식 가동.  둘레 27km 에 이르는 지구상 최대의 실험장치. 다음과 같은 세계를 탐구하는 양성자 - 양성자 충돌장치. E CM = 14 TeV (max) ~ v = c (c= 빛의 속도 ) ~ d = m LHC T he voyage to the ultimate world

Z’

Z’ : Extra neutral gauge boson Exists when there is extra gauge symmetries. U(1) extensions of the SM LR model Other gauge extended models Other species : excited states of Z Little Higgs model Extra dimensional models Underlying Physics

Examples of U(1) extensions E 6 models breaking chain χ model : β=0 ψ model : β=π/2 η model : β=arctan(-√5/3)

LR model Diagonalized to give eigenvalues (W L3, W R3, B) basis

Unknown model parameters are M Z’ Z-Z’ mixing angle Note that where and eigenstates

Z’ couplings to quarks and leptons The Z-Z’ mixing angle is given by Lagrangian for a Z’ in E6 model

e.g. Couplings for E6 inspired models and LR model where

Phenomenology Drell-Yan process Z’

Experimental limits PDG 2008

CDF collab., Phys. Rev. Lett., 95, (2005)

Identification of Z’ using t and b S. Godfrey and T. A. W. Martin, Phys. Rev. Lett., 101, (2008) K q depends on QCD and EW corrections. e.g.

S. Godfrey and T. A. W. Martin, PRL 101, (2008)

Z’ mass and total width Cross section to Forward-backward asymmetry Rapidity ratio Off-peak asymmetry Basic Observables Measuring Z’ couplings at the LHC e.g. F. Petriello and S. Quackenbush, Phys. Rev. D 77, (2008).

Forward-backward asymmetry where Rapidity ratio y1 is introduced to exclude low Z’ rapidity events.

M. Dittmar, Phys. Rev. D 55, 161 (1997)

Detector resolution effects are ignored. Reconstruction efficiency of Z’ production is near 90% from CMS simulation. CTEQ 6.5 NLO PDF used. Integrated luminosity 100fb -1 unless stated otherwise. Factorization and renormalization scale : M Z’ Acceptance Cuts

Differential cross section Parity symmetric couplings Parity violating couplings Calculation

Rewrite the differential cross section Absorbing We have

Define four observables

which are expressed in terms of observables

where We derive the Master equation

e.g. If we let Solving the Master equation to have

Results

If M Z’ =1.5 TeV, 100 fb -1 luminosity and y 1 =0.8 can discriminate the example models with 90% C.L. and 1 ab -1 luminosity (SLHC) will provide precise determination. If M Z’ =3 TeV, 100 fb -1 luminosity and y 1 =0.4 can discriminate some models. For M Z’ =3 TeV, 1 ab -1 luminosity (SLHC) will provide reasonable determination.

Exotic Z’ Generation-dependent couplings Leptophobic Hadrophobic Flavour-violating And more…

W’

W’ : Extra charged gauge boson Exists when there are extra gauge symmetries more than U(1). LR model Other gauge extended models Other species : excited states of W Little Higgs model Extra dimensional models Underlying Physics

LR model (e.g.) Diagonalized to give (W L +, W R + ) basis where

Search for W’ High energy single lepton final states Single top production W’ → l - ν W’ → t b

D0 collaboration, PRL 100, (2008) Transverse mass Edges of transverse mass distribution are crucially related to the mass of W’.

Experimental limits PDG 2008

CDF constraints

D0 observations D0 collaboration, PRL 100, (2008)

Feasibility of W’ at the CMS C. Hof, Acta. Phys. Pol. B 38, 443 (2007) Reference models : same couplings as the SM e.g.

Exotic W’ Left-right asymmetric : coupling constants and CKM Leptophobic Hadrophobic Flavour-dependent SU(2) Exotic gauge self-couplings : W’-W-Z, W’-W’-Z … And more…

H+H+

H + : Charged scalar Exists when there is extra Higgs sector more than SM singlet. 2HD model MSSM and more extensions (NMSSM etc.) LR model Other GUT-based model Underlying Physics

Higgs sector in the LR model Two triplets a bidoublet : breaking of SU(2) R and its L-R partner : electroweak symmetry breaking and fermion masses with VEVs Note that define

Charged Higgs boson in the LR model Mass matrix where Charged Higgs mass Diagonalization by

relevant tbH + couplings similarly for lepton sector

Phenomenology Light charged Higgs from t  H   b at Tevatron Light charged Higgs boson : Absence of observed charged Higgs boson Constrained by

CDF collaboration, PRL 96, (2006)

Pair production of charged Higgs boson at LEP ALEPH collaboration, PLB 543, 1 (2002)

B      and charged Higgs boson R. Barlow, ICHEP 2006

Experimental constraints for LR charged Higgs

allowed D.-W. Jung, K. Y. Lee., Phys. Rev. D 76, (2007)

Light charged Higgs production at the LHC sequential decay after tt pair production 10 8 top quarks produced More than 10 5 charged Higgs expected D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, (2008)

Heavy charged Higgs production at the LHC dominant channel : K-factors for the NNLO QCD corrections considered N. Kidonakis, JHEP 05, 011 (2005).

D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, (2008)

in the LR model in the 2HD model Decay of produced charged Higgs boson

D.-W. Jung, K. Y. Lee., Phys. Rev. D 78, (2008)

Different structure of the Yukawa couplings in the LR model leads to different phenomenology of the Higgs bosons from those of the 2HD model. Production cross section of the charged Higgs in the LR model is generically larger than that of the 2HD model at the LHC. Decays of the heavy charged Higgs boson in the LR model combined with the production cross section might discriminate the LR charged Higgs from the 2HD charged Higgs boson.

H ++

H ++ : Doubly charged scalar appears when there exist Higgs triplets or higher multiplets. LR model model Little Higgs model Higgs triplet model for neutrinos Underlying Physics

H ++ in the LR model Production depends on W R mass Phenomenology depends on neutrino structure and see- saw mechanism. Lepton number violating terms are ∝ m WR

Productions

Decays

Reconstructed pp→H ++ H -- →μ + μ + μ - μ - CMS collab., J. Phys., G 34, N47 (2007)

Expected discovery of pp→H ++ H -- →μ + μ + μ - μ - CMS collab., J. Phys., G 34, N47 (2007)

100% dilepton assumed a. 100 fb -1 b. 300 fb -1 ATLAS collab., J. Phys., G 32, 73 (2006)

q’

t’, b’: Fourth generation quarks Generically heavier than t and b since they are not observed yet. Why not even in the SM? LEP data on invisible decay of Z boson restricts the number of generations =3 : 4 th neutrino should be heavier than m Z /2. Underlying Physics

Why 3 generations? LEP data on invisible decays n = Astrophysical data of He production D.N. Schramm and M.S. Turner., Rev. of Mod. Phys. 70, 303 (1998)

Decays Charged current decays FCNC decays …

Present bounds PDG 2008

Q, L

Excited quarks and leptons : Heavy states of quarks and leptons sharing quantum numbers with ordinary quarks and leptons. Appear in the composite models. Quarks and leptons are bound states of some constituents. (“Preon”) Experimentally similar to 4 th generations. Underlying Physics

Excited fermions can be pair-produced via gauge couplings. If the compositeness scale is high enough, the compositeness manifests through effective 4-fermion contact interactions PDG 2008

Dark Matter

Dark matter : (Large) missing energy at the collider Appears in various models LSP in the MSSM Lightest heavy states in the Little Higgs model Lightest KK states in the extra dimensional model And many other models… Underlying Physics

Many possibilities are open at the LHC. Summary